Palladium currently costs about the same as gold, but during the late 1990s it briefly tripled in price because of the Ford Motor Companies stockpiling of huge quantities of it for use in their catalytic converters. It turned out that improvements in technology reduced the need, and Ford ended up selling their stockpile at a loss. A loss of a billion dollars or so. (See below for an example of what you can do with a catalytic converter.)

While not common, palladium coins have been minted by a number of countries, notably Russia: They are quite beautiful.

Small rectangle of 0.01mm foil, 99.999%
We didn't expect anyone to send us free gold and platinum, but this is pretty close! This small sample was kindly donated by George (not 007) Lazenby, who saw the slashdot discussion. It came in a lovely little plastic vial.
George got this and the other samples he donated at a surplus auction of his high school. It seems he was the only one there who appreciated the erbium foil. This sample and the others he sent had been donated to the school by a former student who worked at NIST (National Institute for Standards and Testing), where they had been used as x-ray calibration standards. This means they are probably very pure.Source:George (not 007) LazenbyContributor:George (not 007) LazenbyAcquired:24 May, 2002Price: DonatedSize: 1"Purity: 99.999%

Sample from the RGB Set.
The Red Green and Blue company in England sells a very nice element collection in several versions. Max Whitby, the director of the company, very kindly donated a complete set to the periodic table table.

Sample from the Everest Set.
Up until the early 1990's a company in Russia sold a periodic table collection with element samples. At some point their American distributor sold off the remaining stock to a man who is now selling them on eBay. The samples (except gases) weigh about 0.25 grams each, and the whole set comes in a very nice wooden box with a printed periodic table in the lid.

Catalytic Converter.
Catalytic converters clean up car exhaust by burning any fuel that didn't get burned up properly in the engine. It's better to emit a little more carbon dioxide and water than to emit unburned or partially burned hydrocarbons, which turn into smog. The converters work by using the unique ability of certain precious metals, notably platinum, palladium, and rhodium, to catalyze the burning of hydrocarbons at temperatures below their normal ignition point.
The exhaust gas is passed through a ceramic honeycomb coated with fine particles of one or the other of the metals, cleaning it up and in the process heating the converter up to a fairly high temperature (which has the useful side effect of making it work better).

To be honest, I have no idea if this particular catalytic converter actually uses palladium rather than one of the other possible metals. I have it under palladium just because of the story about Ford's ill-fated attempt to stockpile palladium for use in their catalytic converters.

I decided to see if I could use this converter to catalytically burn propane from a propane torch. It worked. I started by pointing a lit plumbing torch at the ceramic unit from a new catalytic converter. After it was glowing red hot next to the flame, I turned the gas off long enough for the flame to go out, then quickly turned it back on. Sure enough the ceramic quickly turned red hot again, and depending on how I positioned the unlit torch, the glowing area grew and moved around. It was quite obviously burning the propane, even though there was absolutely no open flame. The fact that there was no smell of propane also confirmed that it was being consumed quite effectively.

To be perfectly clear: In the picture for this sample, the torch is not lit: It is simply sending out a stream of cold propane gas. The ceramic element is consuming the fuel catalytically. There's probably something really useful you could do with this effect.

Here's what the whole cartridge looks like. The converter contains two of these:

Palladium leaf.
Gold leaf you've probably heard of, but it's possible to get very thin sheets of several different pure metals: Click the Sample Group link below to see all the ones I have, which represent pretty much the complete list of those that are commercially available. (Many, many different mixed alloys are also available in leaf form.).

Palladium leaf may seem exotic at first, but it's actually quite commonly used as an alternative to silver, because it looks similar but does not tarnish. For outdoor applications, for example, you cannot use silver leaf. This may be one of the few instances where a truly precious metal (comparable in price to gold) is used to imitate a far less valuable one (silver is usually about 1/70th the price of gold or palladium).

Leaf like this is so thin it has to be picked up with special Red Squirrel hair brushes (none of that Gray Squirrel crap, mind you) and when it wafts down onto an object it conforms to the shape of the surface, settling in even to details as fine as a fingerprint.

Palladium round.
This coin (technically a "round" not a "coin" since it is not legal tender) was very kindly donated by Dan York, a fan of this website. I've been wanting a palladium coin for a long time, but the price has remained stubbornly high. Fortunately Dan came to my rescue with this very generous contribution.Source:Northwest Territorial MintContributor:Dan YorkAcquired:1 August, 2004Price: DonatedSize: 1.5"Purity: 99.95%Sample Group:Coins

Blood sugar test strips.
The package says these contain palladium "for improved accuracy". I am waiting for a call back from their customer service department to explain just exactly where the palladium is, and why. They are strips meant to be used with a blood glucose test meter.Source: Justin UrgitisContributor: Justin UrgitisAcquired:1 August, 2004Text Updated:11 March, 2007Price: DonatedSize: 1.5"Purity: UnknownSample Group:Medical

Ring.
Palladium is potentially a nice metal to use for jewelry: It's less expensive than gold or platinum, and doesn't tarnish like silver. On the other hand, by those measures titanium or stainless steel are better still. But practicality is often not given much weight in jewelry, which may explain the relative scarcity of palladium trinkets.Source:QVCContributor:QVCAcquired:15 January, 2006Text Updated:20 February, 2006Price: $140Size: 1"Purity: >95%

Element coin.
Dave Hamric sells element samples under the name Metallium. He's developed a line of coins struck out of various common and uncommon metals: They are quite lovely, and very reasonably priced, considering the difficulty of creating some of them.
Here is the back side of this coin (click either picture to see it larger):
Click the Sample Group link below to see many other coins made of various elements, or click the link to his website above if you want to buy one like this.Source:Dave HamricContributor:Theodore GrayAcquired:1 December, 2006Text Updated:14 January, 2007Price: $90Size: 0.75"Purity: >99%Sample Group:Coins

Coin or stamp?
Is this a coin or is it a stamp? Hm. Well, let's read the description from the eBay listing:

Each circular postage stamp is imperforated and has a diameter ranging from 1.5 up to nearly 3 inches.

The design of each postage stamp features a coin that commemorates the 1967 Coronation of King Taufa'ahau IV.

The stamps in this lot were officially Overprinted by the government (i.e. an additional printing on a stamp that was not part of the original design) so that the stamps could also celebrating the 50th birthday of King Taufa'ahau IV on 4th July 1968.

So, basically, it's a stamp of a coin, except it's made of actual palladium metal, except it's really only a thin foil of metal on a paper backing. And you'd be insane to stick one on an envelope since they are (a) way too valuable and (b) wouldn't work as postage anyway, except maybe in Tonga.

Concerning the value, the listing says the set weighs 13g, but that includes the paper backing, the weight of palladium is much less.

This is a set of 18 stamps of various sizes, I photographed two of the nicest ones (see following sample).

Antique sponge.
This sample came from the lab of a deceased chemist. Look at the date on it! Rec'd 10-5-27: It's over 80 years old. Fortunately precious metals don't go bad. Sponge, by the way, refers to very finely powdered material with high surface area. It looks like little balls, but if you touched it it would probably be very powdery. Palladium is used as a catalyst where surface area is important, that's probably why it was made into sponge form.
Addition and correction from the source:

Back in the early 20th century, we did not have the monolithic and ubiquitous chemical companies like the Alfa Aesars and Sigma Aldriches we see today, industrial powerhouses manufacturing specialized chemicals for research and laboratories. So, if a professor needed a metal or chemical such as this in a small amount, he (always a he back then) would either have to produce it at the university or laboratory where he was working, or appeal for some samples from a personal contact working one of the few companies dealing with uncommon materials, in this case, precious metals.

Palladium is used as a catalyst where surface area is important, so it may have been produced in sponge form for this reason, but it is more likely that this is the raw palladium directly after it was produced. Most of the laboratory-scale reductions of palladium from one of its compounds and even some variations of the industrial ore refining and isolation process give sponge-type metal, which is then either remelted into a larger ingot or powdered further.

Catalytic converter honeycomb.
Catalytic converters contain two ceramic honeycombs like this. Each is about 2" thick (look at the 3D rotation video to see the sides of it) and contains some mixture of palladium, rhodium, or platinum particles coated on the surface of the ceramic. These particles catalyze (hence the name) the burning of any residual unburned fuel coming out the engine exhaust pipe. I have a Popular Science column that shows how to use one of these to burn propane gas without a flame.Source:Farm & FleetContributor:Theodore GrayAcquired:8 February, 2009Text Updated:8 February, 2009Price: $70Size: 5"Purity: <1%